1.

A piece of wire of Résistance R is cut in to 5 equal parts and these parts are thenconnected in parallel, if the equivalent resistance of these combination is 'x' then theratio of R/x?

Answer»

\bf \underline{Given}:

▪ Resistance of wire: R

▪The piece of wire is cut into 5 equal PARTS.

▪If these (5 equal) parts are arranged in PARALLEL,then the equal resistance becomes x

\bf \underline{To \: find}:

▪ The ratio of R/x

Resistance of each piece of wire after being cut into FIVE equal parts =\sf \dfrac{R}{5} \: \Omega

We KNOW that, in parallel combination :

\sf \implies \dfrac{1}{x} = \dfrac{1}{R_1} + \dfrac{1}{R_2} + \dfrac{1}{R_3} + \dfrac{1}{R_4} + \dfrac{1}{R_5}

\sf \implies \dfrac{1}{x} = \dfrac{1}{\dfrac{R}{5} } + \dfrac{1}{\dfrac{R}{5} } + \dfrac{1}{\dfrac{R}{5} }+ \dfrac{1}{\dfrac{R}{5} }+\dfrac{1}{\dfrac{R}{5} }

\sf \implies \dfrac{1}{x} = \dfrac{5}{R} + \dfrac{5}{R}+\dfrac{5}{R}+\dfrac{5}{R}+\dfrac{5}{R}

\sf \implies \dfrac{1}{x} = \dfrac{25}{R}

\sf \implies \dfrac{R}{x} = 25

So, the ratio of R/x is 25



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